Polycarbonate resins have excellent toughness, impact resistance, thermal stability, self-extinguishing property, dimensional stability, and heat resistance, and accordingly have been used in the manufacture of electro-electronic products such as mobile phone housings, backlight frames, and connectors, among other products. Polycarbonate resins have also been used in the manufacture of automobile parts such as head lamps, instrument panels, and lens, and as a substitute for glass in materials requiring transparency and impact resistance.
However, when a polycarbonate resin is used to manufacture a product requiring transparency, the product can exhibit deteriorated scratch resistance characteristics as compared to glass. Polycarbonate resin can also yellow when exposed to sunlight for a long time.
Polymethylmethacrylate (PMMA) resin has excellent weather resistance and transparency, and excellent adherence and strength such as flexural strength and flexural strain differing from polycarbonate resin. Accordingly PMMA resin can be used as adhesives, lighting materials, and building materials, among other products. However, PMMA has inferior impact strength compared to that of other thermoplastic resins, so it has limited use in the manufacture of thin products with less than a certain thickness requiring sufficient impact strength.
Accordingly, when a transparent PMMA resin having excellent scratch characteristics is alloyed with a transparent polycarbonate resin having excellent toughness, it is expected that the alloy would exhibit both excellent impact resistance and excellent scratch characteristics.
However, as mentioned in Japanese application No. 1993-130731, when the polycarbonate resin is alloyed with the PMMA resin, the molecular weights and weight ratio are limited within a certain range due to the miscibility and refractive index difference between the two resins. When the levels are outside of these ranges, there is a concern that a pearl effect, uneven color, and opaque characteristics may be exhibited.
Accordingly, much research on improving the scratch resistance of polycarbonate has been carried out.
For example, U.S. Pat. No. 4,027,073 discloses a surface treatment method using a Si compound and a method of improving the scratch resistance through acrylic UV coating. In addition, U.S. Pat. No. 5,338,798 discloses a method of using syndiotactic PMMA; U.S. Pat. No. 5,292,809 discloses a method of using a fluorine-substituted bisphenol; and U.S. Pat. No. 4,743,654 discloses single-phase blends of polycarbonate resin and polyalkylmethacrylate.
However, the compounds have problems of high cost and limited application fields.